Phases

Stimulation

A usual precursor to ejaculation is the sexual arousal of the male, leading to the erection of the penis, though not every arousal nor erection leads to ejaculation. Penile sexual stimulation during masturbation or vaginal, anal or oral sexual activity may provide the necessary stimulus for a man to achieve orgasm and ejaculation. With regard to intravaginal ejaculation latency time, men typically reach orgasm 5–7 minutes after the start of penile-vaginal intercourse, taking into account their desires and those of their partners, but 10 minutes is also a common intravaginal ejaculation latency time.[1][2] A prolonged stimulation either through foreplay (kissing, petting and direct stimulation of erogenous zones before penetration during intercourse) or stroking (during masturbation) leads to a good amount of arousal and production of pre-ejaculatory fluid. While the presence of sperm in pre-ejaculatory fluid is thought to be rare, sperm from an earlier ejaculation, still present in the urethra, may be picked up by pre-ejaculatory fluid.[citation needed] In addition, infectious agents (including HIV) often can be present in pre-ejaculate.

Premature ejaculation is when ejaculation occurs before the desired time. If a man is unable to ejaculate in a timely manner after prolonged sexual stimulation, in spite of his desire to do so, it is called delayed ejaculation or anorgasmia. An orgasm that is not accompanied by ejaculation is known as a dry orgasm.

After the start of orgasm, pulses of semen begin to flow from the urethra, reach a peak discharge and then diminish in flow. The typical orgasm consists of 10 to 15 contractions, although the man is unlikely to be consciously aware of that many. Once the first contraction has taken place, ejaculation will continue to completion as an involuntary process. At this stage, ejaculation cannot be stopped. The rate of contractions gradually slows during the orgasm. Initial contractions occur at an average interval of 0.6 seconds with an increasing increment of 0.1 seconds per contraction. Contractions of most men proceed at regular rhythmic intervals for the duration of the orgasm. Many men also experience additional irregular contractions at the conclusion of the orgasm.[5]

Ejaculation begins during the first or second contraction of orgasm. For most men the first spurt occurs during the second contraction. The first or second spurt is typically the largest and can contain 40 percent or more of the total ejaculate volume. After this peak the flow of each pulse diminishes. When the flow ends, the muscle contractions of the orgasm continue with no additional semen discharge. A small sample study of seven men showed an average of 7 spurts of semen (range between 5 and 10) followed by an average of 10 more contractions with no semen expelled (range between 5 and 23). This study also found a high correlation between number of spurts of semen and total ejaculate volume, i.e., larger semen volumes resulted from additional pulses of semen rather than larger individual spurts.[6]

Alfred Kinsey measured the distance of ejaculation, in "some hundred" of men. In three-quarters of men, the semen exuded from the penis, "In other males the semen may be propelled from a matter of some inches to a foot or two, or even as far as five or six and (rarely) eight feet".[7]Masters and Johnson report ejaculation distance to be not greater than 30–60 cm.[8] Distance of ejaculation however, has nothing to do with sexual functioning, as during penetration of penis in vagina the distance of ejaculation plays no role. Dribbling of semen from the penis is usually sufficient for impregnation.

Refractory period

Most men experience a refractory period immediately following an orgasm, during which time they are unable to achieve another erection, and a longer period again before they are capable of achieving another ejaculation. During this time a male feels a deep and often pleasurable sense of relaxation, usually felt in the groin and thighs. The duration of the refractory period varies considerably, even for a given individual. Age affects the recovery time, with younger men typically recovering faster than older men, though not universally so.[8]

However, some men are able to achieve sufficient sexual arousal immediately after ejaculation, and others may have refractory periods of fewer than 15 minutes. A short recovery period may allow them to seamlessly continue sexual play from one ejaculation to sexual stimulation in preparation for the next. However, other men are averse to stimulation during the early part of the refractory period.

There are men who are able to achieve multiple orgasms, with or without the typical sequence of ejaculation and refractory period. Some of those men report not noticing refractory periods, or are able to maintain erection by "sustaining sexual activity with a full erection until they passed their refractory time for orgasm when they proceeded to have a second or third orgasm".[9]

Volume

Ejaculation example

The force and amount of semen that will be ejected during an ejaculation will vary widely between men and may contain between 0.1 and 10 milliliters.[10] (By way of comparison, note that a teaspoon is 5 ml and a tablespoon holds 15 ml.) Adult semen volume is affected by the time that has passed since the previous ejaculation; larger semen volumes are seen with greater durations of abstinence. The duration of the stimulation leading up to the ejaculation can affect the volume.[11] Abnormally low semen volume is known as hypospermia. One of the possible underlying causes of low volume or complete lack of semen is ejaculatory duct obstruction. It is normal for the amount of semen to diminish with age.

Quality

The number of sperm in an ejaculation also varies widely, depending on many factors, including the time since the last ejaculation,[12] age, stress levels,[13] and testosterone. Greater lengths of sexual stimulation immediately preceding ejaculation can result in higher concentrations of sperm.[11] An unusually low sperm count, not the same as low semen volume, is known as oligospermia, and the absence of any sperm from the semen is termed azoospermia.

Development

During puberty

The first ejaculation in males often occurs about 12 months after the onset of puberty, generally through masturbation or nocturnal emission (wet dreams). This first semen volume is small. The typical ejaculation over the following three months produces less than 1 ml of semen. The semen produced during early puberty is also typically clear. After ejaculation this early semen remains jellylike and, unlike semen from mature males, fails to liquefy. A summary of semen development is shown in Table 1.

Most first ejaculations (90 percent) lack sperm. Of the few early ejaculations that do contain sperm, the majority of sperm (97%) lack motion. The remaining sperm (3%) have abnormal motion.[14]

As the male proceeds through puberty, the semen develops mature characteristics with increasing quantities of normal sperm. Semen produced 12 to 14 months after the first ejaculation liquefies after a short period of time. Within 24 months of the first ejaculation, the semen volume and the quantity and characteristics of the sperm match that of adult male semen.[14]

^a Ejaculate is jellylike and fails to liquefy.^b Most samples liquefy. Some remain jellylike.^c Ejaculate liquefies within an hour.

Control from the central nervous system

To map the neuronal activation of the brain during the ejaculatory response, researchers have studied the expression of c-fos, a proto-oncogene expressed in neurons in response to stimulation by hormones and neurotransmitters.[15] Expression of c-fos in the following areas has been observed:[16][17]

Hands-free ejaculation

Although uncommon, some men can achieve hands-free ejaculations, which is an ejaculation without any manual stimulation. Such men usually do it by tensing and flexing their abdominal and buttocks muscles along with vigorous fantasising. Some men do it by relaxing the area around the penis, which may result in harder erections especially when hyperaroused.[18]

Perineum pressing and retrograde ejaculation

Perineum pressing results in an ejaculation which is purposefully held back by pressing on either the perineum or the urethra to force the seminal fluid to stay inside. In such a scenario, the seminal fluid stays inside the body and goes to the bladder. Some people do this to avoid making a mess by keeping all the semen inside.[19] As a medical condition it is called retrograde ejaculation.[20]

Health issues

For most men, no detrimental health effects have been determined from ejaculation itself or from frequent ejaculations, though sexual activity in general can have health or psychological consequences. A very small percentage of men may experience a transient postorgasmic illness syndrome following ejaculation.[21][22]

It is not clear whether frequent ejaculation increases,[23] reduces[24] or has no effect[25] on the risk of prostate cancer.

Two large studies:[26][27][28] "Ejaculation Frequency and Subsequent Risk of Prostate Cancer"[29] and "Sexual Factors and Prostate Cancer"[30] suggest that frequent ejaculation over a lifetime offers some protection against prostate cancer. The US study involving "29 342 US men aged 46 to 81 years"[29] suggest that "high ejaculation frequency was related to decreased risk of total prostate cancer".[29] The Australian study involving "1079 men with prostate cancer and 1259 healthy men" found that "there is evidence that the more frequently men ejaculate between the ages of 20 and 50, the less likely they are to develop prostate cancer".[31]

the protective effect of ejaculation is greatest when men in their twenties ejaculated on average seven or more times a week. This group were one-third less likely to develop aggressive prostate cancer when compared with men who ejaculated less than three times a week at this age.